1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Raspberry Pi 4 firmware reset driver
4  *
5  * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
6  */
7 #include <linux/delay.h>
8 #include <linux/device.h>
9 #include <linux/module.h>
10 #include <linux/of.h>
11 #include <linux/platform_device.h>
12 #include <linux/reset-controller.h>
13 #include <soc/bcm2835/raspberrypi-firmware.h>
14 #include <dt-bindings/reset/raspberrypi,firmware-reset.h>
15 
16 struct rpi_reset {
17 	struct reset_controller_dev rcdev;
18 	struct rpi_firmware *fw;
19 };
20 
21 static inline struct rpi_reset *to_rpi(struct reset_controller_dev *rcdev)
22 {
23 	return container_of(rcdev, struct rpi_reset, rcdev);
24 }
25 
26 static int rpi_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
27 {
28 	struct rpi_reset *priv = to_rpi(rcdev);
29 	u32 dev_addr;
30 	int ret;
31 
32 	switch (id) {
33 	case RASPBERRYPI_FIRMWARE_RESET_ID_USB:
34 		/*
35 		 * The Raspberry Pi 4 gets its USB functionality from VL805, a
36 		 * PCIe chip that implements xHCI. After a PCI reset, VL805's
37 		 * firmware may either be loaded directly from an EEPROM or, if
38 		 * not present, by the SoC's co-processor, VideoCore. rpi's
39 		 * VideoCore OS contains both the non public firmware load
40 		 * logic and the VL805 firmware blob. This triggers the
41 		 * aforementioned process.
42 		 *
43 		 * The pci device address is expected is expected by the
44 		 * firmware encoded like this:
45 		 *
46 		 *	PCI_BUS << 20 | PCI_SLOT << 15 | PCI_FUNC << 12
47 		 *
48 		 * But since rpi's PCIe is hardwired, we know the address in
49 		 * advance.
50 		 */
51 		dev_addr = 0x100000;
52 		ret = rpi_firmware_property(priv->fw, RPI_FIRMWARE_NOTIFY_XHCI_RESET,
53 					    &dev_addr, sizeof(dev_addr));
54 		if (ret)
55 			return ret;
56 
57 		/* Wait for vl805 to startup */
58 		usleep_range(200, 1000);
59 		break;
60 
61 	default:
62 		return -EINVAL;
63 	}
64 
65 	return 0;
66 }
67 
68 static const struct reset_control_ops rpi_reset_ops = {
69 	.reset	= rpi_reset_reset,
70 };
71 
72 static int rpi_reset_probe(struct platform_device *pdev)
73 {
74 	struct device *dev = &pdev->dev;
75 	struct rpi_firmware *fw;
76 	struct device_node *np;
77 	struct rpi_reset *priv;
78 
79 	np = of_get_parent(dev->of_node);
80 	if (!np) {
81 		dev_err(dev, "Missing firmware node\n");
82 		return -ENOENT;
83 	}
84 
85 	fw = rpi_firmware_get(np);
86 	of_node_put(np);
87 	if (!fw)
88 		return -EPROBE_DEFER;
89 
90 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
91 	if (!priv)
92 		return -ENOMEM;
93 
94 	dev_set_drvdata(dev, priv);
95 
96 	priv->fw = fw;
97 	priv->rcdev.owner = THIS_MODULE;
98 	priv->rcdev.nr_resets = RASPBERRYPI_FIRMWARE_RESET_NUM_IDS;
99 	priv->rcdev.ops = &rpi_reset_ops;
100 	priv->rcdev.of_node = dev->of_node;
101 
102 	return devm_reset_controller_register(dev, &priv->rcdev);
103 }
104 
105 static const struct of_device_id rpi_reset_of_match[] = {
106 	{ .compatible = "raspberrypi,firmware-reset" },
107 	{ /* sentinel */ }
108 };
109 MODULE_DEVICE_TABLE(of, rpi_reset_of_match);
110 
111 static struct platform_driver rpi_reset_driver = {
112 	.probe	= rpi_reset_probe,
113 	.driver	= {
114 		.name = "raspberrypi-reset",
115 		.of_match_table = rpi_reset_of_match,
116 	},
117 };
118 module_platform_driver(rpi_reset_driver);
119 
120 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
121 MODULE_DESCRIPTION("Raspberry Pi 4 firmware reset driver");
122 MODULE_LICENSE("GPL");
123